Worksite preparations often include grading a worksite to form a specific, desired slope. Conventional grading may require that multiple grading stakes be placed about the worksite as reference points to ensure that the correct amount of material is removed or added to form the desired grade. The accuracy of the grade slope, however, may be dependent upon the number of grade stakes used and the distance between each grade stake. As the distance between stakes increases, the error in the grade slope may also increase. Accordingly, to minimize error in the grade slope, surveyors place stakes a limited distance apart. Depending on the worksite, stake placement may be a lengthy and tedious process. Further, during the actual grading, additional personnel often are needed to monitor the grade to ensure that the grade is within acceptable limits.
One known system for increasing accuracy of the grade slope without increasing the number of grade stakes uses a laser plane as a reference point, instead of the grade stakes. The laser plane may be emitted over the worksite so that it is parallel to the desired grade. During grading, a work machine may reference the laser plane while excavating the ground or earth in order to create the desired grade.
One laser system is disclosed in U.S. Pat. No. 5,951,613 to Sahm et al. The system disclosed in the '613 patent includes an apparatus for determining the position of a motor grader in a site coordinate system. This system uses a controller, GPS receivers, and several sensors to determine the position of the motor grader in the site coordinate system.
Another system includes a laser plane detecting system for use on a bulldozer type tractor for pushing earth material to grade a worksite. The laser plane detecting system may include a mast attached to the bulldozer blade that detects the position of the laser plane. The laser mast may be associated with the blade in a manner to control the blade so that the mast tracks the laser plane, thereby causing the blade to track the desired grade.
While these known systems are useful for some large excavations, they may be impractical for smaller jobs. For example, some grading may be performed in areas having limited access or that are too small for large work machines. Motor graders and track-type bulldozer tractors may be unwieldy and/or uneconomical to operate at these worksites. In addition, the known systems include a laser mast attached to the blade. Therefore, the systems may be incapable of determining the position of the blade relative to the work machine.
The systems and methods for grading disclosed herein overcome one or more of the shortcomings of conventional systems.